Apparatuses that capture an image of a subject placed in a chassis while illuminating the subject with a light source have conventionally been used in many different application fields. In the field of biochemistry, an imaging apparatus, which uses a chemiluminescent substance or a fluorescent substance as a labeling material and reads out luminescence or fluorescence of the labeling material to detect gene sequences, level of gene expression, separation, identification or molecule weight of protein, or evaluate characteristics, has been known for example from JPA2005-283322.
Concretely, for example, after adding a fluorescent coloring material or fluorochrome, to a solution containing DNA fragments, the DNA fragments are electrophoresed on a gel support. Alternatively, DNA fragments are electrophoresed on a gel support that contains a fluorescent coloring material. Thereafter, the gel support is soaked in a solution containing a fluorescent coloring material, to label the electrophoresed DNA fragment. Then the gel support is irradiated with excitation light to excite the fluorescent coloring material to radiate fluorescent light, and the fluorescent light is captured to produce an image. Based on the subsequent image, a DNA distribution on the gel support is detectable.
In another alternative, DNA fragments are denatured after being electrophoresed on a gel support. Next, the denatured DNA fragments are at least partially transferred to a transfer support such as a nitrocellulose film through the southern blotting method. Then, the denatured DNA fragments are hybridized with a probe, which is preparated by fluorochrome-labeling of such DNA or RNA that is complementary to the target DNA, so that only the fragments of the complementary DNA to the fluorochrome-labeled DNA or RNA probe are sorted to be labeled. Thereafter, the fluorescent coloring material is excited with the excitation light, and the radiated fluorescent light is captured as an image, to detect a distribution of the target DNA on the transfer support.
The above-mentioned prior art captures a luminescent or fluorescent image by converging light from the gel support or the transfer support through an optical system onto an image sensor. However, the chemiluminescent light and the fluorescent light are so feeble and attenuate to such a low level through the optical system that it takes a long exposure time to obtain a satisfactory image even though the optical system uses lens elements of small f-numbers. That is, the optical system adversely affects the sensitivity of the image sensor to the chemiluminescent or fluorescent light in the prior art.
Furthermore, the subject such as the gel support or the transfer support is conventionally placed horizontally in the chassis in order to prevent deviation and improve operability. On the other hand, the optical system and the image sensor are oriented vertically, i.e. perpendicularly to the subject. Therefore, the subject and the optical system need certain spacing between them, which enlarges the height of the apparatus. However, considering recent trend to minimization and lightness of hardware devices of various fields, compactness is desirable also in the biochemical field.